A few reactions!
- I tend to think at some point, all justification when you're doing something apart from, eg, doing a mathematical proof with clearly assumed premises, hits a brick wall, and you have to start somewhere on intuition. If you work hard enough, you can keep questioning the premises science is based on, and to some extent, the fact it works so darn well has to be taken into account. This is where I distinguish being an illogical person from being an unreasonable person.
- When we speak of relativism/not, whatever the formal definition, I get the sense what's really going on is not that people are saying we can believe contradictions, so much as that the "you have to start somewhere" for some topics isn't the same place for everyone. That is, the premises most natural to, e.g., a theory of value meaningful to a given individual, simply may not be the same.
It's no different from saying there might be multiple models of economics, but only one set of laws of physics.
The former are more pragmatic than about pure truth -- we judge them on usefulness/not, based on certain goals one might have. What goals those are might not be set in stone the same for each person.
- Whether morality falls wholly, partly, or not at all in this kind of sphere depends on whether, like science, there's a way to map it canonically to a more logical realm. In physics, this map is provided, afaik by the property that physical quantities (kinda by definition) may be described using math (that's part of what being a quantity is!), which provides a very rigid map from experience to logic.
If value judgment is about a theory of how to act, I think this is far from completely a reductionist endeavor like physics -- if anything, because the future is emergent, there may be many different ways one might act. Whereas the basic parts that constitute reality (the reductionist side) may simply be the same always, so there might not be much to fuss over. This could be seen as the difference between finding the parts vs the many different ways the parts could combine to create new patterns.
Does this mean I think there's a good argument that all moral statements are subjective? Not at all. I tend to think that, to the extent there are pretty reasonable grounding premises which do appear to be universal, e.g. stuff about suffering, there are some moral statements we might as well live by.
I often label this as the difference between basic morality vs the more expansive theory of possible value. I tend to think ways of seeing value do tend to appeal to a subject who experiences reactions to situations, and those reactions suggest various premises to begin with in value judgment.
But I tend to think basic morality seems to be grounded in premises that it seems to me at least many people who reject are more or less being unreasonable.
(E.g. yes you can define morality any way you like, you could say morality = pig food, but if we're honest about what that word generally constitutes, I think there are at least some founding premises/values to build off of without which it's not even clear we're talking about morality.)